128 



HEILBRUNN 



The flowing blood normally contains thromboplastic substances and 

 substances like thrombin, which promote clotting, and substances 

 like heparin and fibrinolysin, Avhich tend to prevent or reverse clotting. 

 Within the intact organism, there is constant danger of blood clot- 

 ting within the vessels as thrombin and thromboplastic substance 

 increase in amount. It is probable that small clots frequently form 

 within the blood stream and are reversed or liquefied before they 

 cause serious damage. Ordinary methods of blood viscometry do not 

 reveal the existence of incipient or partial clots in the blood. For, 

 in order to obtain samples for viscosity tests, the blood is either de- 

 fibrinated or it is treated with anticoagulants. Such treatment 

 would mask the existence of clots within the blood. 



When tissues of the body are injured, beyond much doubt they 

 throw into the circulation injury substances that have a thromboplas- 

 tic action and would therefore tend to induce clotting. This may be, 

 and probably is, a primary factor in the cause of traumatic shock. 

 It would be interesting, therefore, to know how the viscosity of the 

 flowing blood changes folloAving tissue injury. The studies of 

 Knisely (32) clearly indicate that, following trauma, there is a marked 

 increase in blood viscosity, presumably because of incipient or partial 

 clotting. Knisely describes what he calls a sludging of blood as a 

 result of tissue injury. Knisely 's studies are primarily morphological 

 and are the result of microscopic study. They emphasize the im- 

 portance of attempting to make viscosity measurements of blood 

 within the organism or at least without the addition of anticoagulants. 



Although for the past thirty years the interest in protoplasmic vis- 

 cosity has been steadily maintained, there has been no great enthu- 

 siasm for the field. For each paper on the viscosity of protoplasm 

 that has been published, there have been at least dozens on cellular 

 respiration. And this in spite of the fact that the correlations be- 

 tween protoplasmic activity and viscosity appear to be much more 

 satisfactory than any correlations between such activity and respira- 

 tion. This has certainly been shown true in the study of such phe- 

 nomena as cell division, anesthesia, and drug action. The reason for 

 the lack of literature in the field of protoplasmic viscosity is easy to 

 understand. It is hard, at least in animal tissues, to find cells suitable 

 for viscosity studies. Until recently no one has been able properly 

 to measure the viscosity of muscle protoplasm. Fortunately, as 

 noted earlier, Rieser has developed an accurate method for making 

 such determinations (19a). In the future this will doubtless yield 



